Fluid power unit



Feb. 21, 1950 z. D. RUBEN I 2,498,451

FLUID POWER UNIT Filed April 10, 1944 2 Shets-Sheet 1 FIG! l HVVENTOR.

Z ORRO D. RUBEN lay/[WW Feb. 21, 1950 z, RUBEN 7 2,498,451

FLUID POWER UNIT 2 Sheets-Sheet 2 Filed April 10, 1944 Patented Feb. 21, 1950 UNITED STATES PATENT A OFFFICE FLUID POWER UNIT Zorro D. Ruben, Chicago, Ill.

Application April 10, 1944, Serial No. 530,416

This invention relates to power mechanisms in general and more particularly to power mechanisms which include a piston reciprocable in a cylinder for the interconversion of rotary and reciprocatory motion. In its more specific aspects this invention is applicable to pumps, compressors, fluid motors and engines.

It is one of the objects of the present invention to provide a power mechanism wherein the cylinder block with the pistons reciprocating therein is rotatable, and wherein each piston is provided with a yoke that moves with it in its combined rotary and reciprocatory motion, said yoke acting to support the side thrust which would otherwise be communicated to the piston by the driving member.

It is a further object of the present invention to provide an improved arrangement for effecting the interconversion of the rotary and reciprocatory motion, which arrangement will provide for a simple and efilcient valve action in controlling the flow of fluid into or from the cylinder bore.

It is a still further object of the present invention to provide an improved and simple means for varying the output of the power unit as either by varying the stroke of the piston or by a valve control which varies the effect of a constant stroke action of the piston, the desired result being ob- 12 Claims. (Cl. 103-162) the phase relationship of the reciprocatory motion of the piston and the circular motion of the cylinder block with respect to the ports. This phase relationship determines the position and direction of reciprocation of the piston at the moment that the cylinder block opens into communication with a. port and at the moment communication with that port is closed, thus altering the output of the machine.

It is a still further object of the present invention to provide a mechanical construction wherein the cylinder block is driven by a torque tube which surrounds the inclined axial cam that controls the positions of the pistons in the cylinder bores as the cylinder block rotates.

By reason of the present construction it is possible to produce a mechanism such as, for instance, a variable displacement hydraulic pump, which is exceedingly small and light in weight for given operating pressure; especially pumps that operate at very high pressures, such as two thousand pounds per square inch. Also, as a result of the present construction, a small, light,

- high pressure pump may be built wherein the adtained either by varying the inclination of an inclined axial cam that coacts with the pistons, or by varying the timing of the valves with respect to the prsticn of the rotary cylinder block Within which the pistons are reciprocated.

It is a still further object of the present invention to provide an improved connecti0n between a rotary shaft and a rotatable cylinder block carried thereby. In the preferred embodiment of the present invention the mechanism comprises a stationary cylinder casing from one end of which a rotary power shaft extends. Within the casing the power shaft carries a torque tube that extends approximately to the opposite end of the casing and there has a cylinder block secured thereto to be carried b the torque tube. The cylinder block in its rotation brings each cylinder bore thereof successively into communication with intake and discharge ports formed in the stationary part of the structure. In one preferred construction means is provided for varying the angle of inclination of the axial cam to vary the stroke of the pistons, thus varying the output of the mechanism. In another preferred construction the inclination of the axial cam is maintained constant but the cam is angularly adjustable with respect to the intake and discharge ports to vary vantages of a rotary cylinder block are combined with the advantages of a structure wherein the side thrust of the pump piston against the cylinder walls is eliminated by the employment of yokes such as are used on pumps wherein the cylinder block is stationary.

The attainment of the above and further objects of the present invention will be apparent from the following specification taken in conjunction with the accompanying drawings forming a part thereof.

In the drawings:

Figure 1 is a longitudinal sectional view through a pump embodying the present invention;

Figure 2 is a longitudinal sectional view taken along the line 2-2 of Figure 1 and looking in the direction of the arrows;

Figure 3 is an end view of the pump of Figure 2;

Figure 4 is a fragmentary sectional view taken along the line 4-4 of Figure 1 with the outer casing omitted;

Figure 5 is a fragmentary sectional view taken along the line 55 of Figure 1 with the outer casing omitted;

Figure 6 is an end view of a yoke of the pump of Figure 1;

Figure '7 is a side view of the same yoke:

Figure 8 is a view of the cam bearing surface of the swash plate of Figure 1;

Figure 9 is a longitudinal sectional view through a pump of a modifled construction embodying the present invention;

l 'igure 10 is a sectional view taken along the line |8-| 0 of Figure 9; and

Figures 11 and 12 are, respectively, end and side views of one of the yokes used on the pump of Figure 7.

Reference may now be had more particularly to Figure 1. The pump illustrated in Figure 1 comprises a stationary casing body circular in cross section. having peripherally spaced bolt holes 2 for receiving bolts or the like for mounting the pump as desired. A rotatable shaft 3 is journalled in the body I in suitable bearings 4, and is constantly urged in a direction leftward, as seen in Figure 1. by acompressed coiled spring I. A suitable shaft seal 8 held by a threaded nut I is provided, as is usual. Within the body the shaft 3 has a circular flange In on which is splined a torque tube II. To secure the torque tube to the flange Hi the flange is provided with axially extending ribs |3 (Fig. that extend into slots l4 in a short neck l5 formed in the torque tube. The torque tube is thus keyed to and rotates with the shaft 3. At its forward end the torque tube II has a bearing bushing |8 secured thereto in any desired manner as, for instance,by means of a pin 9 (Fig. 2) that holds the bearing bushing flxed in the torque tube. A cylinder block 28 is secured in the forward end of the torque tube, in a manner to be presently described. The cylinder block is star-shaped, having a plurality of arms 2|, in this instance seven, radiating from a central hub, each of which arms has a longitudinally extending cylinder bore 23 therethrough. A cylinder block cover plate 24 is secured to the cylinder block by welding. The cylinder block cover plate 24 is splined to the torque tube. For this purpose the periphery of the cover plate 24 is provided with slots 21 that receive fingers 28 at the end of the torque tube The cylinder block cover plate has openings 29 therein, each of which is located over one of the cylinder bores 23.

A stationary spindle 3| coaxial with the drive shaft 3 extends through the cylinder block cover plate 24 and through the cylinder block and is journalled at its opposite end in a suitable ballbearing 32 in the flange l0 of the drive shaft 3. The spindle 3| has a cam support 33 located in a milled slot 35, being pivotally mounted therein as by a pin 38. A pair of swash plate bearings 38-39 are rotatably mounted on the cam support bearing upon a variable axial cam 40 that is keyed to the cam support 33. The variable axial cam 48 consists of a solid metallic ring or disc that flts over and is keyed to the cam support 33 which is pivoted on the pin 38 carried by the stationary spindle 3|. Each swash plate bearing 38-39 consists of a ring or annulus that is free to turn on the cam support, being loosely fitted on the support and operates in sliding surface contact with the variable axial cam 40.

Each cylinder bore 23 has a piston 44 reciprocable therein. Each piston is part of a piston and yoke assembly that cooperates with the swash plate bearings to effect reciprocation of the piston upon rotation of the torque tube carrying the cylinder block. Each yoke, indicated at 45, is of a construction such as is shown more particularly in Figures 6 and 7. Eachyoke consists of a metal member including inner and outer radial bearing surfaces 48-49 and a tangential bearing surface 58. A thin flexible metal ear 52 is welded to each yoke, said ear having a per- 4 foration l3 therethrough through which extends a piston connecting rod 84. One end of the piston connecting rod is threaded into the piston,

, as may be seen from Figure 1. The opposite end The swash plate bearing 38 has a number .of pockets 88 formed therein, one opposite each piston. A floater pad 68 is located in each pocket between the swash plate and the bearing surface 51 at the end of the connecting rod 54. Each swash plate also has a series of slots III, which admit oil to the bearing surface between the swash plate and the floater pad. The circular floater pad 69 has a flat rear surface which slides in a small ellipse on the swash plate bearing, and has a front surface which is curved to receive the piston rod bearing 51. The swash plate bearing 39 is similar to the bearing 38 and also has a floater pad slidable thereon opposite each piston return bearing 82.

Each yoke bears upon and reciprocates on the inner surface of the torque tube and also slides between the bearing bushing l8 and the cylinder block. The radial and tangential bearing surfaces 4850 slide on the cylinder block as the piston reciprocates, in a manner to be more fully described as this specification proceeds.

The spindle 3| has an axially extending bore therein in which is mounted a control cam I5 near the end of a control shaft 18 that extends through a connecting bushing 11 bolted to a connection cover which is itself bolted to the casing by bolts 8|. The control cam 15 controls the positions of two axially slidable control pins 82-83 that bear against the cam support 33 and flx its variable angle of inclination.

The inner surface of the cover plate 80 has two arcuate grooves 88-8'| therein forming ports or passageways, each of which extends through almost and which communicate with intake and outlet ports 89-90, respectively. The inner surface of the connection cover and the outer surface of the cylinder block cover are around perfectly flat so that the cylinder block cover 24 slides on the inner surface of the connection cover 80, under pressure of the spring 5 aided by the fluid pressure within the cylinders.

An explanation will now be given of the mode of operation of the pump of Figure 1. Rotation of the drive shaft 3 causes rotation of the torque tube II, the yokes, the cylinder block cover plate 24, and the cylinder block 20. The spindle 3| and the axial cam carried thereby are stationary. As the cylinder block and the yokes rotate, the bearing surface 51 of each piston bears against the associated pad 83 on the swash plate and causes the piston to reciprocate. Each piston 54 is moved into the cylinder by the engagement of the bearing surface 51 with its pad 68 whereas the movement of the piston outwardly of the cylinder is eflected by the yoke which is moved by the bearing 62 acted on by its associated pad. The swash plates 38-39 are free to rotate on the variable axial cam 40. The friction between the swash plates and the cam 48 is made very low.

The pressure of the pad or pads on the swash plates causes the swash plates to turn with the cylinder block. One of the contacting surfaces of each swash plate with the cam 40 is shaped to form a tapered land bearing as shown in Figures 7 and 3 of my application Serial No. 490,957. The bearing design is preferably altered to permit rotation in either direction. Each pad, such as 69, has a small elliptical movement in its cavity 69 in the swash plate 38. At the time the piston of any one cylinder commences to move outwardly in its bore the cylinder is in communication with the intake port 86 of the cover plate. When the piston reaches its outermost position the further rotation of the torque tube brings the associated cylinder bore into communication with the outlet port 81 so that upon reverse movement of the piston, that is, movement thereof into the cylinder, it discharges the contents of the cylinder through the discharge port.

To change the delivery of each cylinder per revolution of the drive shaft it is merely necessary to change the inclination of the axial cam 43, since the inclination of this cam determines the stroke of the piston. To change the angle of inclination of the cam it is merely necessary to adjust the control cam shaft 15. When the variable axial cam is in a plane at right angles to the axis of the drive shaft 3 rotation of the drive shaft will produce no reciprocation of the pistons, hence no output of the pump.

Reference may now be had more particularly to Figure 8 showing a modified form of variable delivery pump wherein the stationary axial cam is at a fixed angle of inclination to the axis of rotation of the cylinder block and wherein the pump pistons have a fixed stroke, the variation in intake or delivery being effected by changing the timing relationship between the position of the piston and the opening or closing of the intake and outlet ports. Insofar as the structure of Figure 9 is the same as that of Figure 1 the same reference numerals have been used and a further description thereof is not necessary at this time. In Figure 9 the drive shaft, torquetube and the cylinder block are of the same construction, as in the pump of Figure 1. In this pump a spindle, indicated at III), which is angularly adjustable but is mechanically held stationary during operation of the pump, carries an axial cam III which has swash plates II2--I l3 thereon and freely rotatable thereon. Each piston 44 is provided with a yoke I I6 of a construction such as illustrated more fully in Figures and 11. The yoke IIB of the pump of Figure 9 differs from that of the pump previously described essentially in that each yoke embraces three sides of an arm of the cylinder block rather than only two sides as in Figure 2. For this purpose the yoke I I6 has U-shaped lugs I I1 integral therewith or welded thereto which U-shaped lugs provide radial bearing surfaces I I8I I9 and tangential bearing surfaces I that embrace an arm of the cylinder block. In the pump of Figure 9 the yoke slides in its full length against the inner peripheral surface of the torque tube. The yoke II6 has ears 52-59 the same as the yoke previously described.

The piston rod 54 in the pump of Figure 9 has, at its outer end, a conical bearing surface I at the apex of which there is formed a ball seat or socket that receives a projection at the end of a floater pad I26 that is free to turn on the conical surface I25. The opposite face of the floater pad I26 bears against the swash plate bearing H3 and slides thereon in a small elliptical path.

The valve arrangement in the pump of Figure 9 is identical with that of the pump of Figure 1, the connection cover 80 being provided with fluid passageways the same as is illustrated in Figure 3.

5 Upon rotation of the drive shaft 3 of the pump of Figure 9 the cylinder block is rotated and the stationary axial cam III causes the pistons to reciprocate in the cylinder block, the length of stroke being determined by the inclination of the axial cam. Therefore each piston has a fixed stroke. During the rotation of the cylinder block each individual cylinder bore is alternately brought into communication with the intake port and the discharge port, the timing being determined entirely by the angular position of the cylinder block. In order to vary the output of the pump it is merely necessary to turn the spindle H0. Turning of the spindle IIII counterclockwise, as viewed from the left hand side 01" Figure 9, will cause the piJton 44 to move inwardly within the cylinder bore. Others of the pistons will move outwardly. Thus, while in Figure 9, if rotation of the shaft is assumed to be clockwise, as viewed from the right hand side of Figure 9, the piston 44 is at the end of its outward stroke at the time that the cylinder block has just passed out of communication with the inlet port and is about to pass into communicaion with the outlet port; a counter-clockwise adjustment of the axial cam I I I will change this relationship. When this adjustment has been made the piston will not be quite at the end of its stroke when the intake is closed and will still be making some of its intake stroke even after the discharge port is opened to the associated cylinder bore. Later, during the discharge stroke, the cylinder block will close its communication with the discharge port and open communication with the intake port even before the piston has reached the end of its discharge stroke. Thus only part of the full discharge of the piston will take place while the associated cylinder bore is in communication with the discharge port. By this arrangement the output of delivery of the pump is varied. In order to get zero delivery it is merely necessary to turn the axial cam to such a position that the piston 44 will be in its mid position within the cylinder at the time that the cylinder passes from communication with the intake port to communication with the discharge port. When this condition prevails the piston 44 will draw liquid from the intake port during half of the intake stroke and will draw liquid from the discharge port during the other half of the intake stroke. During the discharge stroke the piston will discharge liquid back into the discharge port during half of the discharge stroke and will discharge liquid back into the intake port during the other half of the discharge stroke. For any other adjustment of the axial cam the piston 44 will be effective for only a fractional part of its full stroke. In view of the fact that the cylinder block contains many cylinders the pistons of which are at any one time at different positions, it may be seen that when the pump is operating at less than 100% capacity each piston may, during the ineffective fraction of its stroke, be delivering liquid to some other cylinder bore rather than to the discharge port. Thus each piston and its associated cylinder bore will act as a pump during a fraction of its stroke and, during another fraction of its stroke will be driven by pressure developed in one or more of the other cylinder bores. Because of the reversal of the direction of pressure I have found it neces- 7 sary that each yoke be provided with the tangen- 7 tial bearing surfaces lit-Ill that bear on opposite sides of the cylinder block arm. This means that the pump of Figure 9 can operate to pump liquids in either direction so that either port 89-90 may be the intake port and the other be a few preferred embodiments of my invention.

It is, however, to be understood that the invention is not limited to the precise constructions here shown, the same being merely illustrative of the principles of the invention. What I considernew and desire to secure by Letters Patent is:

1. Apparatus of the class described comprising a rotatable torque tube, means at one end of the tube for rotating it, a cylinder block secured in the opposite end of the tube and rotatable therewith, a shaft extending axially through the block and around which shaft the block rotates, an inclined axial cam carried by said shaft within the tube, cylinder bores formed in the block around said shaft, pistons in said bores, said block having openings between adjacent bores, and means slidably connecting the pistons with said inclined cam, said means being slidable in said openings and supported on and rotating with the torque tube.

2. Apparatus of the class described comprising a torque tube, means at one end of the tube for rotating the tube, a cylinder block secured to the; opposite end of the tube and rotated thereby, parallel cylinder bores formed in the block, pistons reciprocable in the bores, a stationary ported member against which the block slides, the cylinder bores being brought into and out of communication with the ports as the block rotates, a stationary inclined axial cam within the tube, means slidably connecting the pistons with the cam and means for adjusting the position of the cam during rotation of the torque tube to alter the output of the apparatus per revolution of the cylinder block.

3. Apparatus of the class described comprising a torque tube, means at one end of the tube for rotating the tube, a cylinder block secured to the opposite end of the tube and rotated thereby, parallel cylinder bores formed in the block, pistons reciprocable in the bores, a stationary po'rted member against which the block slides, the cylinder bores being brought into and out of communication with the ports as the blockrotates, a stationary inclined axial cam within the tube, means slidably connecting the pistons with the cam and means for rotatably adjusting the position of the cam with respect to the ports of the ported member while maintaining its axial inclination constant therebyaltering the positions of the pistons in the respective cylinder bores at the instant of covering and uncovering of the ports by the cylinder bores, so that the output of the pump is varied while the piston stroke remains constant.

4. Apparatus of the class described comprising a 8 justably mounting said cam on said shaft for angular adjustment about an axis at right angles to the longitudinal axis of the shaft, and means extending through said shaft for adjusting the angle of inclination of the cam with respect to the longitudinal axis of the shaft.

5. Apparatus of the class described comprising a torque tube, means for rotating the tube, a star-shaped cylinder block secured to one end of the tube and rotated thereby, parallel cylin. der bores formed in the'arms of the star-shaped block, pistons reciprocable in the bores, an inclined axial cam within the tube and means slidably connecting the pistons with'the cam, said means extending between the tube and the respective arms and being supported in and axially sliggble between the cylinder block and the torque tu 6. A paratus of the class described comprising a tube, a star-shaped cylinder block secured to one end of the tube, parallel cylinder bores formed in the arms of the star-shaped block, pistons reciprocable in the bores, an inclined axial cam within th tube, means extending axially through the cylinder block for supporting the cam, and means slidably connecting the pistons with the cam, said means including parts supported in and axially slidable between the tube and the arms of the cylinder block.

7. Apparatus of the class described comprising clined axial cam carried by said shaft within the tube, cylinder bores formed in the block around said shaft, pistons in said bores, means slidably connecting the pistons with said inclined cam, ports for said cylinders, means for turning the cam about the axis of rotation of the torque tube while maintaining its angle of inclination with respect to said axis constant, to alter the position of the cam with respect to the ports, and means for locking said cam in its adjusted position while permitting rotation of the torque tube.

8. A rotary pump comprising a casing, a ported end member closing one end of the casing and having a port opening on the inside of the casing, a rotatable torque tube in the casing, a cylinder block at one end of the torque tube and rotated thereby in sliding engagement with the ported end member, said block having cylinder bores extending from that surface of the block which is in sliding engagement with the ported end member and movable by the rotation of the tube into and out of communication with the port of the member, means at the opposite end of the torque tube for rotating the torque tube, a stationary inclined axial cam entirely within the torque tube between said last named means and the cylinder block, adjustable means extending centrally through the block for supporting and holding the cam in adjustable relationship with respect to the ported member, pistons reciprocable in the cylinder bores, and means for slidably connecting the pistons with the cam whereby the cam causes reciprocation of the pistons upon rotation of the torque tube and the cylinder block, said connecting means including supporting yokes sliding on the torque tube and supporting the pistons.

9. A rotary pump comprising a casing, an end plate member for the casing, said member having a port therein opening on the inside of the easing. a rotatable cylinder block on the inside or the casing and in sliding contact with the end plate member, means for rotating the block, said block having a cylinder bore therein eccentric with respect to the axis of rotation of the block .and which is brought into and out of communication with said port as the block rotates, a piston reciprocable in the cylinder bore, an inclined axial cam in the casing for reciprocating the piston it the cylinder block is rotated, and means for rotatably adjusting the position of the cam with respect to the port while maintaining its inclination constant with respect to the axis of rotation .61 the cylinder block thereby altering the posiitions of the piston in the cylinder bore at the instant of covering and ot uncovering or the port "by the cylinder block, so that the output of the is varied while the piston stroke remains constant.

10. Apparatus oithe class described comprisin: a tube, a plate secured to the tube and extending across one open end of the tube, a starshaped cylinder block located in the tube with its center coincident with the longitudinal axis or the tube, cylinder bores in the respective arms of the star-shaped block, the longitudinal axes of bores being parallel to the longitudinal axis .0! said tubes, said block being secured to said plate, and ports leading to the cylinder bores.

, 11. In combination a star-shaped cylinder block, parallel cylinder bores formed therein, ports leading to the cylinder bores, means formv means including parts extending between and supported in the space between the block and the tube and slidable in said space in a direction paring a radially outwardly extending flange around 1 block and united therewith, a tube within yam-n the block extends and from which the arms or the block are spaced by the flange, the flange being secured to the tube.

allel with the longitudinal axes of the bores.

20830 D. RUBEN.

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